Claude Code's compaction discards data that's still on disk

Source: Dev.to

What happened

Compaction removed physical files that metadata still referenced. This is a metadata↔disk ordering/race condition—deletion happened before durable metadata confirmation, leaving live references to missing data.

Why it matters

• Silent corruption: apps expect compaction to be safe.
• When files disappear while indexes still point at them, you can get lost vectors, corrupted sessions, or errors that only surface under load or during recovery.

Takeaway for builders

• Stop blind deletes.
• Use a retention window and two‑phase deletes (mark → confirm → delete).
• Employ fsync/atomic renames.
• Implement end‑to‑end integrity checks and frequent snapshots.
• Run chaos tests for compaction.

Reference: Claude Code’s compaction discarded data still on disk — bug report & discussion